Non-contact capacitive sensing system for use in toys

ABSTRACT

For toys that respond to touch to trigger a particular response, an activation system utilizes a non-contact capacitive proximity sensing system that permits activation when a finger, lips or other body part is close to a sensing area in the form of a hidden flat conductor under the surface of a toy so that actual touching of the sensor is not required to activate any of the functions of the toy. Low capacitance coaxial cable buried in the toy is used to connect the sensing area to the capacitance detection circuit so that only the capacitance of the sensing area is measured. Proximity sensing activation occurs when there is an increase in capacitance at the sensing area due to the proximity of a body part, with the change in capacitance being detected through the use of an RC circuit in the feedback loop of an oscillator whose frequency decreases when sensed capacitance increases. Self-calibrating techniques involving adaptive threshold adjustment provide for fail safe sensing in all environments and across unit-to-unit component variations, with the thresholds being set each time the toy is turned on, then adjusted over time as necessary. In one embodiment, multiple sensing areas are sequentially addressed through a multiplexing circuit and all audio circuitry is turned off during sensing to prevent capacitance sensing errors.

FIELD OF INVENTION

[0001] This invention relates to non-contact capacitative sensing andmore particularly to its use in toys.

BACKGROUND OF THE INVENTION

[0002] In most toys, a child's interface with an electronic toy isthrough the pressing of switches. This results in a rather unnaturalinteraction with said toy in order to elicit the desired electronicresponse, such as having to squeeze a doll's hand instead of holding it,or having to press down on a stuffed animal instead of stroking its fur.

[0003] One way to overcome this drawback is through the use ofcapacitive sensing to sense human touch. Capacitive sensing has beenused in many toys in the past to sense touch using conductive areas onthe surface of the toy. The basic premise of this technology is thatwhen the conductive area is touched, the capacitance from the personincreases the capacitance of the conductive area, which can be sensed inmany different ways. The problem with this technology is that aconductive area on a toy is not desirable visually or tactilely. Forexample, it is difficult to put external conductive sensing areas on astuffed animal with soft fur, or on the face of a doll, without it beingvisually and tactilely unappealing. Another disadvantage with this typeof touch sensing is that having the conductive areas external to the toymakes it much harder to pass CE ESD immunity standards. Because the userhas direct access to the internal circuitry through these conductiveareas, it is quite easy to disrupt and/or damage the circuit with staticdischarge. Another disadvantage with having conductive sensors onsurfaces of dolls is that when children dress the doll in clothes, ithides the conductive areas, rendering them useless.

[0004] Another method of proximity sensing which has been used in toysis the sensing of a special stylus which is wired to the toy itself. Onedrawback to this method is that if the wire to the stylus ever breaks orbecomes intermittent through metal fatigue, the toy is rendered useless.Also, for younger children who haven't learned to write with a pencil,the use of a stylus as a pointing instrument is awkward.

[0005] Another method used by toys to sense the user's “touch” withoutthe use of switches is through the use of light-sensing elementsembedded within the doll. When the person's hand covers thelight-sensing element, the decrease in light level is interpreted as a“touch”. The disadvantage of this technology is that any object thathappens to block light to the area is falsely interpreted as a “touch”.

SUMMARY OF THE INVENTION

[0006] This invention also uses capacitive sensing, but differs from theprior art in the fact that the conductive surface is buried inside atoy, and the surface is standard molded plastic, rubber, simulated fur,cloth, or paper, commonly used in toys. The sense areas are undetectablefrom the outside of the toy, so the visual aesthetics of the toy andtactile textures are preserved. Note that the human body has thin skinand large amounts of fluid inside. Thus, a human body part such as afinger is a relatively good conductor inside the skin, which acts like abag of water with a thin dielectric covering. The body part thus makes arelatively good capacitor to earth ground. Even though the sensing areais referenced to its own ground, which is the negative terminal of oneof the batteries, it has some coupling with earth ground as well. Sowhen a human body part that acts like a capacitor to ground comes closeto the sensing area, which is one plate of a capacitor, it changes thefrequency of the an RC-controlled oscillator inside the toy enough to beable to detect it.

[0007] Thus, the capacitive sensing used is proximity sensing of humanskin rather than touch sensing. This proximity sensing must sense muchsmaller changes in capacitance than standard touch sensing because ofthe finite distance between the conductive sensing area and the humanskin. Also, this method must be very cost-effective in order to bepractical for low-cost toys. This type of sensing allows very natural,intuitive interaction with a toy to reliably trigger an electronicresponse. For example, a child kissing a doll's cheek or a young toddlerpointing at a letter can be detected by the electronic toy and canelicit the desired response.

[0008] In one embodiment, in a self-calibrating sequence when the toy isturned on, the entire capacitive threshold for each sensing area isfirst set to zero. A capacitive reading is then taken for each sensingarea. This reading is the capacitance in terms of the number ofoscillator pulses in a predetermined time period.

[0009] If there is no change in sensed capacitance over the appropriatenumber of tries, a threshold corresponding to the number of oscillatorcounts is stored. It is against this stored value that subsequentsamples of the sensing area are tested. A body part near the sensingarea will cause the capacitance to rise, and the oscillator frequency tofall, which results in a decreased number of oscillator pulses and thusa decreased count. When this count is beneath the previously setthreshold by a predetermined amount or delta, then a ‘touched’ conditionis triggered, and the toy responds appropriately.

[0010] For self-calibration, the capacitance threshold is adaptive inthe sense that if the count representing the capacitance sensed is abovethe previously established threshold for a long enough period, then thethreshold is reset to this value.

[0011] Thus for instance, if the sensing area is in the hand of a dolland the child is grasping the hand of the doll when the system is turnedon, then the initial threshold will reflect a capacitance of the sensingarea plus body part. Later, when the sensing area is sampled and thechild is no longer clutching the hand of the toy, the capacitance willgo down and the count of oscillator pulses will go up. If this occursfor a number of cycles, then the threshold is incremented to this newhigher number.

[0012] Note that a finger, lips or other body part can be sensed whenthe body part is non-contacting, for instance, ¼-inch away from thesensing area. This means that the sensing area can be buried beneath theskin of the toy and even underneath synthetic fur in the case of a teddybear, with the toy's actions being triggered by proximity of the bodypart. Thus, unsightly sensing areas are eliminated, making the toy muchmore appealing.

[0013] In summary, for toys that are to respond to touch to trigger aparticular response, an activation system utilizes a non-contactcapacitive proximity sensing system that permits activation when afinger, lips or other body part is close to a sensing area in the formof a hidden flat conductor so that actual touching of the toy is notrequired to activate any of the functions of the toy. Low capacitancecoaxial cable buried in the toy is used to connect the sensing area tothe capacitance detection circuit so that the system is shielded fromcapacitance other than at the sensing area. Proximity sensing activationoccurs when there is an increase in capacitance at the sensing area dueto the proximity of a body part, with the change in capacitance beingdetected through the use of an RC circuit in the feedback loop of anoscillator whose frequency goes down when sensed capacitance goes up.Self-calibrating techniques involving adaptive threshold adjustmentprovide for fail safe sensing in all environments and acrossunit-to-unit component variations, with the thresholds being set eachtime the toy is turned on, then adjusted over time as necessary. In oneembodiment, multiple sensing areas are sequentially addressed through amultiplexing circuit and all audio circuitry is turned off duringsensing to prevent capacitance sensing errors.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] These and other features of the subject invention will be betterunderstood in connection with the Detailed Description in conjunctionwith the Drawings of which:

[0015]FIG. 1 is a diagrammatic illustration of one embodiment of thesubject invention in which a child is kissing the cheek of a doll havinga sensing area located beneath the skin of the check, also showingburied coaxial cable coupling a sensing area to detection circuitrywithin the doll;

[0016]FIG. 2 is a top view of a sensing area which is a small piece ofcopper tape in this embodiment, to which the center conductor of acoaxial cable is soldered;

[0017]FIG. 3 is a block diagram of the subject system indicating lowcapacitance coaxial cable connecting sensing areas through amultiplexing circuit to an oscillator, the output of which is coupled toan external event counter within a micro-controller that counts thenumber of positive-going pulses from the oscillator within a certainpredetermined period of time, which is stored as the sensed capacitance;

[0018]FIG. 4 is a simplified schematic representation of theSchmitt-trigger RC oscillator and a single sensing area when it isselected by the multiplexer of FIG. 3, the sensing area acting as avariable capacitance to ground in parallel with the fixed capacitance ofthe coaxial cable, PCB, and semiconductor components, there being afixed resistor which forms an RC circuit in the feedback path of theSchmitt-trigger inverter which causes the circuit to oscillate at afrequency inversely proportional to the total capacitance; and,

[0019]FIG. 5 is a simplified flow chart showing the programming of themicroprocessor of FIG. 3.

DETAILED DESCRIPTION

[0020] This proximity-sensing scheme involves both the capacitancesensing areas themselves, the circuitry used to detect a small change incapacitance, as well as the wiring used to connect the two.

[0021] Referring now to FIG. 1, what is depicted is a child's toy in theform of a doll, here illustrated at 10, in which the doll has a numberof sensing areas 12 underneath the skin of the doll. In this embodiment,the sensing areas are in the feet, hands, stomach, eyes, mouth, andcheeks of the doll. Each of these sensing areas is fitted with buriedcoaxial cables shown in dotted outline at 14 to connect the sensingareas to the control circuitry of the doll.

[0022] Also shown is a child generally indicated at 16 using her lips18, to activate the doll to perform one of a number of functions bykissing the doll on the cheek. Other types of functions may be activatedwhen the child's body part is adjacent to the other sensing areas sothat the doll can be made to respond in different manners to increasedcapacitance sensed at different sensing areas.

[0023] It will be noted that the sensing areas are buried within theskin of the doll, as are the lengths of coaxial cable to couple thevarious sensing areas to control circuitry carried within the doll.

[0024] Referring to FIG. 2, one such sensing area is illustrated asincluding a strip of copper tape 20 to which the center conductor 22 ofa coaxial cable 24 is soldered as illustrated at 26. This inexpensiveand simple sensing area comprises a sensor which can be used in theproximity sensing described above.

[0025] Referring to FIG. 3, a number of sensing areas 30, 32, 34 and 36are coupled via low capacitance coaxial cable 40 to a multiplexingcircuit 42 shown symbolically as having a number of taps 44 contactedthrough a wiper arm 46 to a common tap 48. Each of these contact pointsis connected to the center conductor of the associated coaxial cable,with a resistor R connected between the center conductor of this coaxialcable and the output of an oscillator 50. In one embodiment, thisoscillator is a Schmitt-trigger inverter acting as an RC-controlledoscillator. It will be appreciated that the frequency of the outputpulses generated by this Schmitt-trigger inverter are inverselyproportional to the capacitance at point 44 of the selected tap, withthe output of the oscillator coupled to an external event counter 56within a micro-controller 58, with the micro-controller controlling theaddressing of the sensing areas as illustrated by signals 60. In thisembodiment, the micro-controller has an associated 6-megahertz crystal68 and a speaker 70 for an audio output, should such be desired.

[0026] The microprocessor continually scans each of the sensor areasusing the multiplexer to select each one sequentially. When a body partcomes into proximity of a sensing area, micro-controller 58 can sensethe increase in capacitance of the particular sensing area and cause thetoy to respond in a preprogrammed way, depending on the sensing areaactivated. For instance, if the user touches the doll's lips, the dollmay be made to make a kissing sound, emanating from speaker 70.Additionally there are many types of movements or sounds that the dollcan make, depending on what is preprogrammed into micro-controller 58.

[0027] Referring to FIG. 4, oscillator 50 has as its output a frequencywhich is inversely proportional to the total capacitance. The totalcapacitance is the sum of the variable capacitance C_(v), and the fixedcapacitance C_(f). Fixed capacitance C_(f) is due to the capacitance ofthe low capacitance coaxial cable, circuit board, and other electricalcomponents in the circuit, whereas C_(v) is variable and depends uponthe proximity of a body part near a sensing area. The RC circuit isformed by a fixed resistor R in the feedback path of the Schmitt-triggerinverter oscillator such that the frequency of the output of theoscillator is changed by variable capacitor C_(v) due to the proximityof a human body part to the sensing area.

[0028] In operation, the capacitance sensing areas are small conductivesurface areas made of conductive tape, copper-clad-PCB, flat copperbraid, or any of the many available low-cost conductive materials usedin electronics manufacturing. The material can be chosen based on cost,manufacturability, and the tactile quality desired. If the sensing areais to be used in a plush stuffed animal, for example, the sensing areashould be soft and malleable, such as copper tape or flat copper braid,as to be undetectable from the outside when the stuffed animal issqueezed. The surface area used in the preferred embodiment isapproximately one square inch.

[0029] Another feature of the subject invention is the method by whichthe above sensing areas are wired to the detection circuitry, which inone embodiment is on a central circuit board in the toy. The sensingareas are likely to be spread out all over the toy, and may be overtwelve inches from the circuit board. Low-capacitance coaxial cable,such as low-cost standard 75-ohm video coax cable, can be used. Thecenter conductor of the coax cable is used to connect the capacitivesensing area to the detection circuitry. The outside shield of the coaxcable is connected to ground, and this prevents the detection circuitryfrom detecting false capacitance changes due to human skin near thecabling itself. This method keeps the capacitance sensing localized tothe sensing area only.

[0030] The detection circuitry must be able to reliably sense very smallchanges in capacitance at the remote sensing area, usually a fewpicofarads. This small increase in capacitance is a small percentage ofthe total capacitance of the coax cable, input capacitance of thedetection circuitry, and stray capacitances on the circuit board. Itwould be possible for a very fast micro-controller to time how long ittakes to charge this capacitance through a resistor with fine enoughresolution to detect this small change in capacitance.

[0031] However, the preferred embodiment of the invention uses an RCoscillator scheme to allow a low-speed, low-power micro-controller todetect this small change. In the illustrated embodiment,micro-controller 58 allows oscillator 50 to run for a pre-determinedamount of time, and counts how many low-to-high transitions occurred.This allows the minute difference in oscillator frequency to add up overmany cycles, making it easy for a slower micro-controller to accuratelydetect the percentage of change in the capacitance.

[0032] The detection circuitry consists of a single Schmitt-triggerinverter acting as the RC oscillator 50, which oscillates at a frequencyinversely proportional to the capacitance that it is connected to. Thereis an analog multiplexer 42 which selects which sensing area isconnected to the oscillator. A transistor circuit in an emitter-followerconfiguration on each sense area may be used which acts as an analogbuffer in order to greatly reduce the impedance so that the largecapacitance of the analog multiplexer does not affect the oscillationfrequency. The output of oscillator 50 is connected to the externalevent counter 56 input on the micro-controller. Note that a low-dropoutregulator may be used which regulates the voltage to the analogoscillator/multiplexer circuit and the micro-controller. This helps tokeep the oscillator frequency from drifting over time, and reacting tonoise on the battery supply. All of the components used in the circuitare commonly available, mature, low-cost components.

[0033] The software algorithm used in the micro-controller in thepreferred embodiment is described in the flowchart of FIG. 5.

[0034] Referring now to FIG. 5, this flow chart represents thealgorithmic operation of the subject system. In the flowchart andelsewhere, the term ‘PAD’ is used to refer to a sensing area, and thetwo terms are interchangeable. Also, the term ‘touched’ is used toindicate when a person's skin is near enough to the sensing area totrigger the capacitive sensing mechanism. The person doesn't necessarilyhave to be ‘touching’ the sensing area for this to occur, since it isproximity sensing. However, the word ‘touched’ is used throughout thispatent in order to make it easier to understand.

[0035] The capacitance reading that will be referred to in FIG. 5reflects the actual capacitance at the sensing area, and is thereforeinversely proportional to the actual number of oscillations counted bythe microprocessor. The microprocessor sets the multiplexer to selectthe sensing area in question, then counts the number of oscillationsbased on its capacitance in a predetermined period of time, then takesthe inverse of that count to arrive at the capacitance reading. Forexample, assume that the counter is an 8-bit counter, the predeterminedperiod is 1 ms (one millisecond), and that a particular PAD has aquiescent ‘untouched’ capacitance such that it oscillates at 200 kHzwhen the PAD is connected to the RC oscillator. When the microprocessorselects this PAD using the multiplexer, it will read a count of 200 whenit counts for 1 ms. In one embodiment, the microprocessor could subtractthis count from the 8-bit maximum, 255, in order to arrive at a‘capacitance’ reading, in this case a value of 55. When this PAD istouched, the capacitance will rise, and cause the oscillator frequencyto fall, let's say to 180 kHz. Now, when the microprocessor takes areading of this PAD, it will get a count of 180 in 1 ms. Subtractingthis from 255, it would arrive at a ‘capacitance’ reading of 75. Asshown in this example, the capacitance reading as referred to in FIG. 5reflects the actual capacitance of the sensing area, not the RCoscillation frequency or the raw oscillation count.

[0036] More particularly, the micro-controller starts up in a power-upblock 80, then advances to a threshold initialization block 82, wherethresholds of all of the sensing areas are initialized to the maximumvalue. Next, the microprocessor advances to a multiplexer initializationblock 84, where it selects the first of the sensing areas. In this case,the first pad is selected. As can be seen by block 86, the capacitivesensing algorithm is inhibited if audio is currently being playedthrough a speaker. If audio is not currently playing, the counter isallowed to count the external pulses from the oscillator during a giventime interval, as illustrated at 90. The algorithm prevents readingsfrom being taken while a sound is being played through the speaker sothat any electrical noise created on the board due to high currentspikes from the audio playback do not give false readings.

[0037] As illustrated in block 90, the current reading is saved, and ata decision block 94, it is ascertained if the capacitance reading forthe current pad is less than the pad's calibrated threshold. It shouldbe noted that the thresholds for all sensing areas are initially set tothe maximum value, so that block 94 is always true when the toy has justbeen turned on.

[0038] If, as illustrated at block 94, the current capacitance readingfor the given pad is smaller than its threshold, this indicates that thethreshold may need to be reset. It is first determined if there wereenough readings below the threshold to warrant a new threshold value, asseen in block 122. This debounce feature of requiring X number ofconsecutive readings below the threshold is utilized to prevent a singlenoisy reading from erroneously adjusting the threshold. If there hasn'tbeen X number of consecutive readings below the threshold, then this padis marked as ‘untouched’, and the threshold value is unchanged, asillustrated in block 112. If there has been X number of consecutivereadings below the threshold, then this pad is marked as ‘untouched’,and the current capacitance reading is established as the new thresholdas seen in block 124, and the process iterates back.

[0039] In order to ascertain if the current pad is being ‘touched’, adetermination is made at block 98 whether the current reading is abovethis pad's threshold by a given amount. If so, the pad is marked asbeing touched.

[0040] As illustrated in block 98, what constitutes a sensing area beingtouched is that the current reading minus the current threshold islarger than a predetermined delta value. If so, then the PAD isconsidered ‘touched’, as illustrated at 100. The delta value being setto a large enough constant so that the system is not triggered by noise,which causes minor changes in the sensed capacitance readings. It shouldbe noted that this delta value may be set to a different value for eachsensing areas. This is useful for deliberately setting the touchsensitivity differently on the various sensing areas. In block 98, ifthe current reading is not larger than the threshold, or the differenceis less than the predetermined delta, then the pad is marked as‘untouched’ as indicated at 112 and at the micro-controller proceeds toblock 102.

[0041] Below is an example of how the threshold initially adjusts to thequiescent capacitance of each sensing area, and why the continualadaptive threshold algorithm is important. When the unit is first turnedon, all thresholds are set to maximum value. At this time, each PAD isalways going to have a reading that is less than the threshold in block94. This is how the system automatically stores the initial quiescentsettings for each pad. For instance, let's assume that the currentcapacitance reading is 100 on the left hand of the doll, the thresholdstarts at 255. The microprocessor will continually read 100 for the lefthand sensing area until block 122 is true, and 100 is now set as the newthreshold value to which all subsequent readings of the left handsensing area is compared.

[0042] The adaptive threshold algorithms is also important in the casewhen, for instance, the left hand of the doll is touched when the unitis first turned on. The quiescent ‘untouched’ reading should be 100, butthe sensing area repeatedly returns a reading of 120 because the lefthand is being held by the child, so the threshold gets set to 120. Whenthe child lets go of the hand, the reading will jump down to 100 andstay there. When that happens, the algorithm notices that the reading isless than the stored threshold, and the ‘untouched’ reading of 100 willnow correctly be stored as the new threshold.

[0043] In one embodiment, even if a PAD is determined to be ‘touched’,it is not acted upon immediately. All of the PADS are read in a singlescanning cycle before the appropriate response is determined. Thisscheme allows for multiple-PAD detection. For example, if only one handis touched, the doll may say “I love to hold hands with Mommy”, but ifboth hands are held, the doll may react differently, for example, bysinging “Ring around the Rosie”. Block 102 checks to see if all of thePADS have been read, and if not, the next PAD is selected in block 108and the reading process is repeated. If at block 102, it is determinedthat all PADS have been read, then block 104 resets the multiplexer tothe first PAD. Block 106 takes into consideration which PAD orcombination of PADS were marked as ‘touched’, and triggers theappropriate response.

[0044] In summary, the subject invention has sensing areas that candetect when human skin is in close proximity. All sensing areas areinside of a toy, where it is visually and tactilely undetectable by theuser. Moreover, the software algorithm self-calibrates all of thesensing areas each time it is turned on, so the absolute capacitance ofa given sensing area, its cabling, and detection circuitry areirrelevant. Moreover, The sensitivity of each area can be setseparately.

[0045] While the subject system has been described in connection withits use within a doll, it will be appreciated that the subject system isuseful anywhere that proximity sensing is required. It will be notedthat the system may be activated by a person's finger or other body partwhich is spaced from the actual sensor itself. This makes burying of thesensors for whatever reason practical so that a covering or other layerof material may be interposed between the sensor and the body part doingthe activation of the system.

[0046] Having now described a few embodiments of the invention, and somemodifications and variations thereto, it should be apparent to thoseskilled in the art that the foregoing is merely illustrative and notlimiting, having been presented by the way of example only. Numerousmodifications and other embodiments are within the scope of one ofordinary skill in the art and are contemplated as falling within thescope of the invention as limited only by the appended claims andequivalents thereto.

What is claimed is:
 1. In a battery-operated toy, a system for sensingthe proximity of a human body part to a sensing area at said toy for theactivation of a selected toy response, comprising: A non-contactcapacitance sensing unit within said toy including an electricallyconductive sensing pad, a proximity sensing circuit for the activationof said toy response and a means for connecting said pad to saidproximity sensing circuit, whereby said pad may be buried beneath theouter covering of said toy to avoid unsightly visible activationapparatus.
 2. The system of claim 1, wherein said means for connectingsaid pad to said proximity sensing circuit includes a shieldedconductor, whereby capacitance sensing is localized to changes incapacitance at said pad.
 3. The system of claim 1, wherein said toyincludes multiple pads distributed about said toy and wherein saidproximity sensing circuit includes a multiplexer for sequentiallyaccessing said pads.
 4. The system of claim 1, and further including anautomatic calibrating unit for sensing capacitances absent the proximityof a body part and for setting a corresponding capacitance thresholdlevel, the calibrating unit being self-adaptive.
 5. The system of claim4, wherein said proximity sensing circuit includes an RC-controlledoscillator and a counter coupled thereto, the frequency of saidoscillator being inversely proportional to the capacitance associatedwith said pad, and wherein said automatic calibrating unit has saidcorresponding capacitance threshold level established by the count insaid counter.
 6. The system of claim 1, wherein said selected toyresponse is a predetermined sound, and wherein said toy has a soundgenerator for generating said predetermined sound when activated by saidtoy, and further including means for inhibiting said proximity sensingcircuit when said sound generator is activated, thereby to eliminate anyfalse readings of capacitance due to the electrical noise of said soundgenerator during capacitance sensing.
 7. The system of claim 4, whereinsaid calibrating unit is activated when said toy is turned on toestablish said capacitance threshold level.
 8. The system of claim 5,wherein said calibrating unit includes means for adaptively setting saidcapacitance threshold level.
 9. The system of claim 8, wherein saidmeans for adaptively setting said capacitance threshold level includes aunit for setting said capacitance threshold level to a maximum value,means for taking a current capacitance reading, means for ascertainingif the current capacitance reading is less than said threshold and meansresponsive thereto for saving the current capacitance as the newthreshold level.
 10. The system of claim 9 and further including meansfor establishing if the current capacitance reading is larger than saidthreshold by a predetermined margin and for activating said toy responseresponsive thereto.
 11. A non-contact capacitance sensing system,comprising: an electrically conductive patch; a length of coaxial cablehaving a center conductor coupled to said conductive patch; anRC-controlled oscillator coupled to said coaxial cable and having anoutput frequency inversely proportional to the capacitance associatedwith said patch; a counter coupled to the output of said oscillator; anda threshold circuit coupled to the output of said counter for indicatingthe presence of a body part adjacent to said patch when the count fromsaid counter varies from said threshold, whereby the adjacency of saidbody part to said patch is sensed.
 12. Apparatus for triggering apredetermined response in a toy, comprising: a non-contact capacitiveproximity system having a conductive pad for sensing the proximity of abody part adjacent said pad; and, a threshold circuit for generating atrigger when the proximity of a body part is sensed.
 13. The apparatusof claim 12, wherein the threshold set by said thresholding circuit isadaptively set.
 14. The apparatus of claim 13, wherein said adaptivelyset threshold is set when said toy is turned on.
 15. The apparatus ofclaim 14, wherein said adaptively set threshold is further adjustedafter the original setting when said toy is turned on.
 16. The apparatusof claim 15, wherein capacitances associated with said pad areperiodically monitored, with said threshold being adaptively set whensensed capacitance associated with said pad is sufficiently differentfrom a previously established threshold.
 17. The apparatus of claim 16,wherein said threshold is reset if the current sensed capacitance islower than that associated with said threshold, whereby a capacitancethreshold that is set during the proximity of a body part is adjustedupon removal from proximity of said body part from said pad.